Transformer



May 14, 1929. BRAND 1,713,214

TRANSFORMER Filed July 11, 1928 v Inventor:

Frederick FTBrand;

His Attorney Patented May 14, 1929'.

UNITED STATES 1,713,214 PATENT OFFICE.

FREDERICK 1. BRAND, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TRANSFORMER.

Application filed July 11,

structed in accordance with the invention,

the windings being shown partially in section to reveal details.

The transformer shown in the drawing includes a magnetic core 1 of theusual three legged type with a central winding leg and two outer legs toprovide return paths for the magnetic flux. The central winding leg issurrounded by a high voltage winding 2 having two end terminals 3 and 4for connection to a high voltage outside circuit. The trans formeroperates as an autotransformer, the winding 2 having a third terminal 5spaced from the end terminal 3 to give the desired voltage for a lowvoltage outside circuit connected to the terminals 3 and 5. The endterminal 3 is grounded.

- An intermediate point, preferably the center, of the winding 2 isconnected to the core 1 by a connection 6 so that the potential of thecore is the same as that point in the high voltage winding 2 to which itis connected. -The core must, of course, be insulated from ground forthis voltage.

The winding 2 has a common section between the terminals 3 and 5 and aseries section between the terminals 4 and 5. The turns of the windingare arranged along the winding leg of the core substantially in theorder of increasing voltage from the low voltage or grounded terminal 3to the high voltage terminal 4. This arrangement avoids high voltage andthe necessity for excessive insulation between adjacent turns and coilsof the winding but results in a wide separation of the common and seriessections of the winding. To avoid an otherwise excessively high reactionbetween the common and series sections of the winding 2, thereis,provided a coupling winding having two sections 7 and 8 surroundingthe winding leg'of the core and which are connected in series by theconductors 9 and 10. The section 8 of the cou- 1928. Serial No. 291,988.

pling winding surrounds the winding leg of the core between it and thehigh voltage windmg 2 so that this section 8 of the coupling winding isclosely coupled to the entire high voltage winding 2 including both itscommon and series sections. The section 7 of the coupling winding islocated at the low voltage end ofthe high voltage winding 2 between thecommon section of the high voltage winding and the adjacent yoke of thecore. This section 7 of the coupling winding thus provides additionalmagnetic coupling between the coupling winding and the common section ofthe main high voltage winding and therefore between the two sections ofthe high voltage winding.

The core 1 is connected by a conductor 11 to the coupling winding andpreferably to an intermediate point at or near the center of thiswinding. This establishes the relative potentials of the core and thecoupling winding, and limits the potential difference between them atany point to a small value because the voltage of the coupling windingitself may be small. Only a small amount of insulation is thereforenecessary between the coupling winding and the core and also between thecoupling winding and the central portion of the high voltage winding 2.

The voltage between the high voltage winding and the coupling windingand core increases gradually from a minimum at the center of the highvoltage winding to a maximum at each end of the high voltage windingwhere this difference in voltage is equal to one half the total voltageof the high voltage winding. The insulation for the high voltage windingtherefore tapers from a small amount at its center to a maximum at eachend and may consist of a suitable arrangement of insulating cylinders 12and end collars and flanges 13. It will be apparent that, even thoughone end of the high voltage winding be grounded no part of the entiretransformer structure requires more insulation than is necessary for avoltage greater than one half that between the high voltage windingterminals. The arrangement is not only economical in insulation but thewindings and core may be comparatively close together so that thereactance is small.

The invention has been explained by describin and illustrating areferred embodiment t ereof but it will e apparent that changes may bemade without departing from the scope of the invention as defined in theappended claims.

What I claim as new and desired to secure by Letters Patent of theUnited States, 1s:

1. A transformer including a magnetic core having a high voltagewinding, said winding having two end terminals and an intermediateterminal for autotransformer connection to two outside circuits, and anauxiliary winding magnetically coupling the common and series sectionsof said high voltage winding, said high voltage winding having one endgrounded and an intermediate point-thereof conductively connected tosaid core. 7

2. A transformer including a magnetic core having a high voltagewinding, said winding having two end terminals and an intermediateterminal for autotransformer' connection to two outside circuits, and anauxiliary winding magnetically coupling the common and series sectionsof said high volta e winding, one end of said high voltage winding beinggrounded, and said core being insulated from ground and conductivelyconnected to an intermediate point of said high voltage winding.

1 3. A transformer including a magnetic core having a high voltagewinding, said winding having two end terminals and an intermediateterminal for autotransformer connection to two outside circuits, and'anauxiliary winding conductively connected to said core and magneticallycoupling the common and series sections of said high voltage winding,one end of said high voltage winding being grounded, and said core beinginsulated from ground and conductively connected to an intermediatepoint of said high voltage winding.

4, A transformer including a magnetic core having a high voltagewinding, said winding having two end terminals and an intermediateterminal for autotransformer connection to two outside circuits, anauxiliary winding magnetically coupling the common and series sectionsof said high voltage winding, said auxiliary winding being conductivelyconnected to said core and disposed between the core and said highvoltage winding having one end grounded and an intermediate pointthereof conductively connected to said'core, and insulation between saidhigh voltage winding and said auxiliary winding and core, saidinsulation progressively increasing in amount from said intermediatepoint of the high voltage winding toward both ends thereof.

In witness whereof, I have hereunto set my

